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Abstract

Background

Research suggests that food intolerance may be a precipitating factor for migraine
like headaches.

Aim

To evaluate the effectiveness of the ELISA (Enzyme Linked Immuno-Sorbent Assay) Test
and subsequent dietary elimination advice for the prevention of migraine like headaches.

Design

Randomised controlled trial.

Setting

Community based volunteers in the UK.

Participants

Volunteers who met the inclusion criteria for migraine like headaches and had one
or more food intolerance were included in the study. Participants received either
a true diet (n = 84) or a sham diet (n = 83) sheet. Participants were advised to remove
the intolerant foods from their diet for 12 weeks.

Main outcome measures

Number of headache days over a 12 week period (item A MIDAS questionnaire). Other
measures includes the total MIDAS score and total HIT-6 score.

Results

The results indicated a small decrease in the number of migraine like headaches over
12 weeks, although this difference was not statistically significant (IRR 1.15 95%
CI 0.94 to 1.41, p = 0.18). At the 4 week assessment, use of the ELISA test with subsequent
diet elimination advice significantly reduced the number of migraine like headaches
(IRR 1.23 95%CI 1.01 to 1.50, p = 0.04). The disability and impact on daily life of
migraines were not significantly different between the true and sham diet groups.

Conclusions

Use of the ELISA test with subsequent diet elimination advice did not reduce the disability
or impact on daily life of migraine like headaches or the number of migraine like
headaches at 12 weeks but it did significantly reduce the number of migraine like
headaches at 4 weeks.

Trial registration number

Keywords:

headache; diet; food elimination; randomised controlled trial

Introduction

Migraine is a condition associated with a severe one sided headache [1,2], which may be accompanied by nausea [3], vomiting, diarrhoea, blurry vision and photophobia [4]. Approximately 6-7% of men and up to 20% of women report experiencing migraine headaches
[1]. It is considered by some that severe migraine can be as disabling as quadriplegia
and is the cause of many General Practitioner (GP) consultations [5]. As well as having an impact on quality of life, migraine has a significant economic
impact, with migraine sufferers requiring 4-6 bed rest days per year [6,7].

The aetiology of migraine attacks is not completely understood [8]. However, a number of precipitating factors have been identified in the literature
including change in stress levels, excessive afferent stimuli, altered sleep patterns,
weather change, and food [5,8].

The role of food in migraine has been a topic of scientific research since the early
1900s. Early studies found that elimination of specific foods from a person's diet
could prevent the onset of a migraine or reduce the number of symptoms experienced
[9,10]. More recent research suggests that food hypersensitivity (intolerance) may be a
precipitating factor for migraine attacks [11] and about 25% of migraine patients report that their symptoms can be initiated by
certain foods [12]. However, the role of food in migraine is still controversial. Unfortunately, the
quality of the research (e.g. study design and sample size) generally in this field
has not been very high [13-16]. Currently, the best accepted method for diagnosing and confirming food hypersensitivity
is empirical, by elimination diet and challenge [17]. This method is laborious, and it is difficult to test all the combinations of food
types that may be causing the problems. Previous studies which have looked at testing
for food intolerance have focused on the presence of IgE antibodies, the "immediate
response" [18,19]. An alternative approach would be to measure food specific IgG antibodies which characteristically
exhibits a slower response [18,20]. The presence of food-specific IgGs may indicate a potential sensitivity to that
particular food, previous studies have shown a relationship between IgG and food hypersensitivity
[21-23]. Food specific antibody levels can be measured through the use of an Enzyme Linked
Immuno-Sorbent Assay (ELISA), in the form of a simple blood test. The use of this
test as the basis of food elimination diets is controversial with little evidence
to support its use for migraines. A small cross over trial (n = 30) participants using
ELISA testing has recently been reported, which demonstrated a significantly reduced
frequency of headache days among a group of patients recruited from a headache clinic
(27). In this study we undertook a further RCT of ELISA testing in a real life setting.

Methods

The study was a single blind, two arm randomised controlled trial in which participants
were randomised to either a "true" diet or "sham" diet control group. Participants
were allocated to one of the two diet sheets based on a randomisation schedule developed
using a random computer number generator by an independent data manager. Simple randomisation
was used with no restrictions (e.g. blocking and/or stratification) placed on the
randomisation. All participants and staff at YorkTest Laboratories were blinded to
group assignment for the duration of the study.

Identifying participants

Participants were recruited through advertisements and a press release. An advert
for the trial was placed in the Migraine Action Association newsletter and on the
University of York's webpage. Additionally there was a press release to the local
media. Participants who expressed an interest in taking part in the study between
March and June 2008 were sent further details about the study, a baseline questionnaire
and a consent form. Because the participants were recruited through advertisement
and through the completion of a postal questionnaire we could not be certain that
all of them had a clinical diagnosis of migraine. Consequently, those recruited to
the study did have self reported headaches that were 'migraine like'. Whilst most
of the participants are likely to have had migraines it is possible that some did
not. All participants aged 18-65, who had a self-reported diagnosis of migraine for
at least 12 months, had no evidence of any other significant co-existing pathology
and experienced 2 or more migraine like attacks (or 4 or more headache days) in the
previous 4 week period were eligible for the screening phase. We wanted to recruit
participants who were having regular migraines or migraine like headaches in order
to maximise the power of the study.

At screening, potentially eligible participants were sent a pin prick test kit, supplied,
at no cost, by YorkTest Laboratories Ltd (York, UK), with only a numerical identifier.
Participants were asked to follow the instructions of the pin prick test in order
to supply a small blood sample. Participants were asked to return this blood sample
directly to YorkTest Laboratories. YorkTest Laboratories carried out an ELISA test
to detect the presence of IgG antibodies specific to a panel of 113 different food
antigens (see Table 1). Participants who had one or more food intolerances identified from the ELISA test
were eligible for inclusion in the study. The cut-off used to determine food-specific
IgG antibodies are detected or not was 10 AU (arbitrary units) per millilitre (AU/ml)
of blood. Most of the 113 foods were tested individually. There were some that were
tested as mixers (e.g., melon mix includes watermelon, honeydew and Cantaloupe melon).
Participants were asked to remove all the foods in that particular mix (if appropriate).
The test is CE marked and test reproducibility meets the requirements of the European
IVD Directive. Participants who showed no evidence of food sensitivity in the ELISA
test were excluded from randomisation and were informed of their true test results.

Treatment and control group interventions

For each participant two diet sheets were generated by YorkTest Laboratories - a true
diet sheet and a sham diet sheet. The sham diet sheet asked participants to eliminate
the same number of foods to which they exhibited IgG antibodies but not those particular
foods. The diet sheets were matched for the number of foods to be eliminated and also
for the difficultly of eliminating foods. YorkTest Laboratories sent the true and
sham diet sheets for each participant to the York Trials Unit, again with only a number
for identification.

Participants were sent the appropriate diet sheet and were advised to remove foods
to which they showed a positive reaction from their diet for a period of 12 weeks.
At the end of this phase of the study, both groups were asked to reintroduce, in a
stepwise fashion, the foods which they had been asked to eliminate. Participants were
asked to reintroduce one food at a time on a weekly basis and continue with the food
if no migraine or migraine like headache occurred. Food reintroduction occurred over
a 4 week period with all eliminated foods (if no migraine or migraine like headache
had occurred) being introduced in the final week. Participants were advised to stop
consuming any reintroduced food if a migraine or migraine like headache occurred and
to continue to reintroduce one of the other remaining foods. At the end of the follow
up period all participants were told which diet sheet they had been given. Participants
were sent the appropriate diet sheet to commence diet elimination in September 2008.

Measurements

The baseline questionnaire recorded information about participants experience with
migraine, including: frequency of migraines or migraine like headache in the previous
4 weeks (number of headache days), symptoms experienced, migraine medication use,
whether they have previously excluded foods from their diet, and any consultations
with healthcare professionals about their migraine or migraine like headache. The
questionnaire also included a measure of disability using the MIgraine Disability
Assessment Scale (MIDAS) [24] and impact on daily life using the Headache Impact Test (HIT-6™) [25,26]. Baseline questionnaires were sent out to participants at the beginning of July 2008.
Reminders were sent 3 weeks later if participants had not returned their original
questionnaire. Participants were followed-up at 4 weeks (October 2008) and 12 weeks
(December 2008) after starting their allocated diet with a short questionnaire which
included the MIDAS, HIT-6 and an additional question asking if the participant had
consulted with a GP about their migraine or migraine like headache over the past 4
or 8 weeks depending on the timing.

The MIDAS questionnaire assesses headache-related disability. Respondents are asked
to answer five questions, scoring the number of days, in the past 3 months, that they
have had activity limitations due to headaches. Two additional items (A and B) are
also included which ask about the number of headaches over the past 3 months and how
painful the headaches were. The Headache Impact Test (HIT) is a tool to measure the
impact headaches have on a person's ability to function on the job, at home, at school
and in social situations. Respondents are asked to answer six questions covering aspects
of functioning mostly impacted by headache: pain, role functioning (the ability to
carry out usual activities), social functioning, energy or fatigue, cognition, and
emotional distress. The responses on each question are described on a 5-point Likert
scale including: never, rarely, sometimes, very often and always.

Participants in both groups completed a daily diary for the 12 weeks they were in
the food elimination phase of the trial. The diary recorded whether or not they had
a migraine or migraine like headache, the duration of the migraine or migraine like
headache, the treatments they used and a migraine/headache severity score (0 to 10
where 0 is no pain and 10 is pain as bad as it can be). Participants in the "true"
diet group were also asked to record their adherence to the diet each day in the diary.
Participants were asked the following question: "Have you followed the study-related
dietary advice today?". If participants answered "yes" to the question 70% of the
time they were categorised as "adhering to the diet most of the time."

Sample size

In a population survey of migraine sufferers it was found that on average patients
had 13 migraines or headache days over a 12 week period (our follow-up period) with
a standard deviation of 11 [24]. We sought a reduction of 5 headache days. Assuming a standard deviation of 11 this
results in a standardised effect size (difference in means/standard deviation) of
0.45. This reduction of a 0.45 of a standard deviation was similar to that observed
in a recent acupuncture trial for migraine prevention [2]. To detect this effect size, assuming 80% power, an independent samples t-test and
a 2-sided 5% significance level we required 78 participants per group, 156 in total.
Allowing for 10% loss to follow up we required a total of 174 participants (87 per
group).

Statistical analysis

The primary outcome measure was the number of headache days over a 12 week period
(item A on the MIDAS questionnaire) which was calculated by summing responses on the
4 and 12 week questionnaires. A headache day was defined as any 24 hour period in
which the patient reported that they had had a migraine attack which lasted more than
4 hours. Secondary outcome measures were the total MIDAS score and total HIT-6 score.
The total MIDAS score was calculated by summing the total number of days from questions
1 to 5 (ignoring A and B). The HIT-6 scores were calculated by assigning a value of
6 to a response of "Never," 8 to "Rarely," 10 to "Sometimes," 11 to "Very Often,"
and 13 to "Always;" these values were then summed. Scores can range from 36 (lowest
possible score) to 78 (highest possible score).

All analyses were conducted on an intention to treat bases, including all randomised
patients in the groups to which they were randomised. Analyses were conducted in SAS
(version 9.1) and SPSS (version 15). We compared the number of migraines in the intervention
and control groups using negative binomial regression models with adjustments for
baseline scores. These models are used to estimate the number of occurrences of an
event when the event has Poisson variation with over-dispersion. We also used a negative
binomial regression model to compare the total MIDAS scores in the intervention and
control groups with similar adjustments for baseline scores. A linear regression model
was used to compare the total HIT6 scores between the intervention and control groups
after adjustment for baseline scores. Stricter levels of significance were used (p
= 0.01) for secondary outcomes to compensate for multiple testing. Multiple imputation
was used to account for the missing data. Five imputations were created using a set
of appropriate imputation models constructed using variables that were predictive
of the missing data (e.g. age, baseline number of headache days) and the group allocation.
Multiple imputation was performed using the mi procedure in SAS with the assumption
that the data were missing at random.

Results

Recruitment of participants and their flow through the study is illustrated in Figure
1. In summary, between March 2008 and June 2008, 289 interested participants contacted
York Trials Unit to register their interest in the study. Of the 289 questionnaires
sent out, 245 (85% of interested participants) returned the questionnaire to be assessed
for eligibility. Seventy eight participants were not randomised into the study as
they did not meet the inclusion criteria, they withdrew consent, they did not return
a blood sample for testing or they did not have any food intolerance identified by
the ELISA test. A total of 167 participants (68% of eligible participants) were randomised,
83 to the sham diet and 84 to the true diet. At 12 weeks follow-up, 71 of the 83 participants
in the sham diet group and 67 of the 84 participants in the true diet group returned
their questionnaires (83% response rate).

Primary outcome

The primary outcome was the number of headache days reported over the 12 weeks of
diet elimination and was available for 69 of the sham and 69 of the true diet group
(Table 4). The median number of headache days in the sham diet group was 20 (IQR = 12 to 29)
and in the true diet group was 19 (IQR = 8 to 28). There was no significant difference
in the reduction of migraines in the true and sham diet groups at 12 weeks (IRR 1.15
95% CI 0.94 to 1.41, p = 0.18). Similar results were found when multiple imputation
was used to account for the missing data (IRR 1.17 95% CI 0.96 to 1.42, p = 0.11).
When the data were analysed for the number of headache days at 4 weeks there was a
significant difference between the two groups (sham n = 78, median = 8, IQR = 5 to
12; true n = 78, median = 7, IQR = 4 to 10; IRR 1.23 95% CI 1.01 to 1.50, p = 0.04).
The finding was consistent when multiple imputation was used to account for the missing
data (IRR 1.24 95% CI 1.02 to 1.50, p = 0.03).

Secondary outcomes

Secondary outcomes were the MIDAS and HIT-6, as can be seen from Table 5. Overall there was no significant difference between the true and sham diet groups
in terms of disability as measured by the MIDAS or impact on daily life as measured
by the HIT-6. The findings remained the same when multiple imputation was used to
account for the missing data.

Discussion

The use of the ELISA test to identify raised levels of IgG antibodies against tested
foods with subsequent diet elimination advice reduced the number of migraines or migraine
like headaches by 23% over 4 weeks. For our primary outcome measure, the results indicated
a small decrease in the number of migraines or migraine like headaches over 12 weeks,
although this difference was not statistically significant. We found little or no
evidence that use of the ELISA test with subsequent diet elimination advice reduced
the disability or impact on daily life as measured by the MIDAS and HIT-6 questionnaires.

Strengths and weaknesses

We believe that this is the largest randomised controlled trial to investigate the
use of diet elimination based on the presence of IgG antibodies for the prevention
of migraine or migraine like headache. The use of ELISA testing has been investigated
for IBS [18] and more recently for migraines [27]. One of the criticisms of the IBS trial was that the food eliminated from the sham
diet did not appear to be as difficult as the true diet. In this study we tried to
address this criticism and we feel that the comparability of the two diets was achieved.
A potential weakness of the current trial, was that attrition was greater than we
had originally anticipated (at 12 weeks n = 138, 17%). Another potential weakness
of the study is that we recruited participants who self-reported their migraines.
Hence, it is possible that they were not suffering from migraines but other forms
of headache, which would not be amenable to dietary manipulation. Furthermore, some
participants suffering from migraine or migraine like headache in our trial will not
have been amenable to dietary manipulation as they will have suffered other 'triggers'
for their migraines or headaches. The previous trial of diet elimination based in
IgG testing for migraine [27] found a difference of 2.73 days at 6 weeks whilst we found a difference of 1 day
at 4 weeks. The smaller effect in our study may have been explained by the fact our
trial was more pragmatic and we did not provide dietary support for participants and
we may have included some in the study who did not have 'true' migraines. Furthermore,
because of low adherence with some participants not keeping to the recommended diet
this would dilute any treatment effect. Nevertheless, despite this our findings do
support this earlier trial.

Although food intolerance has been identified in the literature as a precipitating
factor for migraine, it is one of many factors and the onset of a migraine may be
triggered by either the intolerant food(s) or the combination of precipitating factors.
However, other factors such as menstrual status, body mass index or ethnicity will
have been balanced across by our use of randomisation. Vaughan [8] highlights few migraine patients can become headache free by dietary manipulation
alone, therefore other precipitating factors need to be identified in order for them
to be managed effectively [28]. In addition, for patients to experience any benefit from removing intolerant foods
from their diet they obviously need to adhere to the diet change. The issue of adherence
is further complicated by how aware a patient is of the use of their excluded food(s)
in processed foods or when dining out. For example, mayonnaise may contain egg yolks,
mustard, cornflour/maize starch, all three ingredients are possible foods that a patient
could be asked to eliminate from their diet. To adhere to the diet a patient would
need to read all food labels carefully to identify if the food contains any of their
intolerant foods or ask at each dining establishment they ate at.

Within the current study only 52% of the participants in the true diet group returned
their daily food diary. Whilst adherence was high among this group we do not know
what it was like among the non-responders. Consequently, we were unable to assess
the impact of adherence with the diet within the present study. Future research in
this area needs to ensure that participants adherence with the dietary intervention
is measured using a different tool rather than collecting this information through
daily food diaries. Participants had to 'self-test' which is how this test is used
in a real life. We could not be completely sure that samples related to the participant.
However, it would seem unlikely that many, if any, participants would send another
person's sample back.

Within the current study, all of the participants were informed that they would be
given their true test results at 12 weeks, which may have led some participants, with
more challenging diets, to wait until they knew their 'true' results before persevering
with their diet. On the other hand, our participants were all volunteers so may be
more highly motivated than the 'average' headache patient.

Conclusion

In conclusion, use of the ELISA test with subsequent diet elimination advice did not
reduce the disability or impact on daily life of migraines or migraine like headache
or the number of migraines or migraine like headache at 12 weeks but it did significantly
reduce the number of migraines or migraine like headache at 4 weeks. It might be that
the avoiding the use of a sham may improve compliance as participants will know that
they are allocated to a true diet and respond better to dietary advice.

Future trials in this area need to build in additional nutritional support for participants
to aid adherence and need to identify a suitable tool to measure adherence with the
dietary intervention.

Ethical approval

The study was approved by the Research Governance Committee in the Department of Health
Sciences, University of York, York, UK. Written informed consent was given by all
participants.

Authors' contributions

NM designed the study, coordinated the study and drafted the manuscript. CEH performed
the statistical analyses and helped to draft the manuscript. SJ performed the statistical
analyses. MH, JA and IW helped to draft the manuscript. DJT conceived of the study
and helped to draft the manuscript. All authors read and approved the final manuscript.

Competing interests

The authors declare that they have no competing interests.

Acknowledgements

The study was supported by the York Trials Unit, University of York, York, UK and
by a small grant from YorkTest Laboratories, York. YorkTest provided the pin prick
test and carried out the ELISA test at no cost to the study. YorkTest played no part
in the conception of the study, data collection, analysis, or writing the article.
Dr Gill Hart for her comments on the final draft of the manuscript. Dr Peter Horlock
for managing the testing of the samples provided.